[dreamcompiler]

That's a good link.

Summary: DC is always a bit more efficient than AC. The reason our grid is AC is because high voltage transmission is much more efficient than low voltage transmission.* But you don't want multi-thousand volt feeds coming into your house, so voltage conversion is necessary. If you don't have power electronics, you have to use magnetic transformers to convert between voltages, and magnetic transformers only work on AC. Thus our electric grid is mostly AC.

Now that we have power electronics we can convert voltages without magnetic transformers, and AC is no longer a requirement except for backward compatibility.

*unless you have superconducting cables